Cosmetic compositions, especially foundations, are commonly used to give the skin an aesthetic colour, but also to hide skin imperfections such as redness and/or marks. In this regard, many formulations have been developed to date.
In this respect, there is a growing interest in cosmetic products that provide a change in color in response to external incentives such for example shear force.
Generally, this purpose is achieved by including in cosmetic composition microencapsulated colorants wherein, upon application on the skin, the composition provides the expected changing color. More particularly, the change of color is provided by the colorant-containing microcapsules, which upon rupture by application of a mechanical force, release the entrapped colorant into the composition, thereby changing its color. A mechanical action such as rubbing spread the topical composition and facilitates its penetration into the skin. The immediate change of color of the composition provides a visual esthetical effect.
Different types of entrapped colorants and more particularly pigments-containing microcapsules are already available. They mainly differ through the type of entrapping material(s) and/or the type of encapsulation.
Thus, as pigments encapsulated by microcapsules in acrylic acid and/or methacrylic acid polymers or copolymers, it may be cited for example microcapsules containing copolymer of ethyl acrylate/methacrylic acid ammonium salts, commercialized by the Tagra company and described in WO-A-01/35933. It may be also cited the encapsulated pigments commercialized by TAGRA BIOTECHNOLOGIES under the name BLACKCAP1©, YELLOWCAP1©, REDCAP1©, BLACKCAP3©, YELLOWCAP3©, REDCAP3©.
As pigments encapsulated by microspheres in cellulose derivatives, it can be cited for example spheres comprising cellulose, hydroxypropyl methylcellulose, commercialized by the Induchem company under the name Unisphere©.
As pigments encapsulated by microcapsules in polymers of polyester, polyaminomethacrylate, polyvinylpyrrolidone, hydroxypropylmethylcellulose, shellac types and mixtures thereof, it may be notably cited those described in the application US 2011/0165208 of Biogenics and commercialized under the name Magicolor© by Biogenics.
As other pigments encapsulated by microcapsules may also be cited the ones disclosed by DAITO in JP2011-79804 may be also cited the pigment-encapsulated double-layer microcapsules comprising three or more of the following (a) mannitol, (b) hydrogenated lecithin, (c) polymethylmethacrylate, (d) cellulose and (e) shellac.
These double-layer microcapsules do not comprise an uncoloured core as the one of the microcapsules preferably used according to the invention, but rather a colored inner layer containing the aforesaid components which are mixed all together and then granulated.
However, with some colorant-containing microcapsules it may be difficult to permanently retain the colorant over long periods of time and when subjected to different environments and conditions. This is true of pigments, oil soluble dyes, and water soluble dyes. Thus, some microcapsules described in patents and publications have been found to gradually release the colorant, or to “bleed”, over time when tested for prolonged periods at elevated temperatures. Color bleed occurs when a dye or pigment migrates through or off of microspheres/microcapsules through contact with moisture and/or other ingredients in a formulation such as alcohols or glycols, surfactants, silicones, oils, preservatives, salts and other components typically found in cosmetic formulations. Leeching or bleed of the colorant in cosmetic composition can impair the long term visual effect of the cosmetic both in the container and on the substrate.
Furthermore, some pigment-containing microcapsules may confer a lower coverage effect than expected.
Furthermore, some pigment-containing microcapsules are immediately broken down at the time of application so, while there is the fun of a sudden colour change, it has not been possible to realise intermediate stages in this colour change or to adjust the colour gradation.
Furthermore, some pigment-containing microcapsules may have some stability issues depending on the cosmetic composition and with associated solvents/ingredients.
Furthermore, some pigment-containing microcapsules may have a grey color aspect that confers a not attractive color in the bulk of the cosmetic composition.
At last, some microcapsules may provide a discomfort and/or unfavourable feeling when the cosmetic formulation including them is applied on a keratin material.